1. Field of the Invention
The present invention relates to network communications and, more specifically, to protection path sharing.
2. Description of the Related Art
Advances in wavelength-division multiplexing (WDM) related technologies have started to allow for routing and networking at the optical layer of communications networks, providing a migration toward true optical-layer networking. Optical-layer networking associated with mesh-connected optical networks creates the need for routing wavelength demands over the mesh optical networks and an equivalent need for service recovery in the optical domain in the event of failures.
Traditionally, fast recovery services have been considered an integral part of a transport network, while data networks (e.g., Internet Protocol (IP) networks) were primarily targeted to achieve “best-effort” services. However, with the increasing use of data networks to carry time-critical data (e.g., voice-over-IP (VoIP) data), resiliency and fast recovery of service is becoming an important feature of data networks as well.
With the explosion of IP traffic, traffic engineering of IP flows has become important. To address traffic engineering, label-based switching techniques have been specified that allow an ingress node to route “beneath” the IP routing mechanism. These techniques effectively allow tunneling of IP traffic between ingress and egress nodes in a network transparent to the IP routing protocols and allow for traffic engineering and the bypassing of failed or congested links. One such technique, known as multiprotocol label switching (MPLS), is defined in Rosen, E., Viswanathan, A., and Callon, R., “Multiprotocol Label Switching Architecture,” RFC 3031, January 2001 (herein “RFC 3031”), incorporated herein by reference in its entirety. An alternative such technique, known as IP-over-ATM is discussed in ATM Forum Specification, Multi-Protocol over ATM v1.0, July 1997 (herein “MPOA”), also incorporated herein by reference in its entirety.
While MPLS and related protocols provide a mechanism for directing or engineering traffic in data networks, the issues of use of such protocols for efficient recovery management in data networks continue to present a challenge to network operators.